Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session A73: Remote and multi-qubit entanglement in superconducting systems |
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Sponsoring Units: DQI Chair: James Teoh, Yale University Room: Room 405 |
Monday, March 6, 2023 8:00AM - 8:12AM |
A73.00001: Driven-dissipative remote entanglement for superconducting qubits (Part I): Directional Approach Abdullah Irfan, Xi Cao, Mingxing Yao, Andrew Lingenfelter, Andrew Pocklington, Yuxin Wang, Aashish A Clerk, Wolfgang Pfaff Stabilizing entanglement between remote qubits is of fundamental interest, and a crucial resource for quantum networks. Most approaches to generate remote entanglement make use of gate and measurement operations to generate entangled states, which then can deteriorate over time due to decoherence. In contrast, a dissipatively stabilizing protocol could relax the system into an entangled steady state that becomes the new ground state of the distributed system. In part I of this two-talk series, we analyze and extend an existing proposal by Stannigel et al. [1]; there it was shown that continuous driving can stabilize remote entanglement between a pair of qubits connected through a nonreciprocal waveguide. We extend this scheme by coupling each of the qubits to one or more additional qubits in a chain configuration and show that the steady state of the system is formed by independent Bell pairs of remotely entangled qubits, providing an exciting route toward efficient entanglement purification. We analyze our proposal in the context of superconducting qubits and show that experimental realization is within reach. Our results demonstrate a powerful approach toward robust remote entanglement generation for superconducting qubit networks and modular quantum processors.
[1] K Stannigel et al 2012 New J. Phys. 14 063014
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Monday, March 6, 2023 8:12AM - 8:24AM |
A73.00002: Driven-dissipative remote entanglement for superconducting qubits (Part II): General Strategies Mingxing Yao, Andrew Lingenfelter, Andrew Pocklington, Yuxin Wang, Abdullah Irfan, Xi Cao, Wolfgang Pfaff, Aashish A Clerk Remote entanglement is a fundamental resource for a variety of tasks in quantum information processing; there is thus immense interest in methods for dissipatively preparing and stabilizing such states. While there is considerable work on stabilizing just a single entangled pair of qubits, the potential for stabilizing larger entangled states also exists. Here, we build on the results presented in Part I of this talk, and discuss more general (but nonetheless realistic) strategies for dissipative entanglement stabilization of large numbers of remote qubits, including schemes that do not require any sort of directional interaction. By exploiting subtle symmetry properties, we show that a variety of multi-qubit entangled states can be stabilized, using minimal resources (e.g. correlated loss from a waveguide, local driving, and passive XY couplings). We also discuss the robustness of our schemes to various kinds of imperfections. Our ideas are compatible with superconducting circuit architectures, as well as other experimental platforms (e.g. trapped ions). |
Monday, March 6, 2023 8:24AM - 8:36AM |
A73.00003: Position-dependent excitation of transmon qubits embedded in a 3D waveguide Romain Albert, Maximilian Zanner, Eric I Rosenthal, Sílvia Casulleras Guàrdia, Mathieu L Juan, Konrad Lehnert, Oriol Romero-Isart, Gerhard Kirchmair By embedding superconducting qubits into a microwave rectangular waveguide, it is possible to exploit the combination of short-range direct qubit interactions and long-range waveguide mediated interactions to model a wide variety of Hamiltonians [1]. This unique platform has great potential for quantum simulation, however the intrinsic dispersion of these waveguide and its potential impacts on the qubits has yet to be fully experimentally studied. Recently it has been shown [2] that it is possible to generate self-focusing pulses thanks to this non-linear dispersion relation which can theoretically be used to selectively control a qubit. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A73.00004: Absorbing a Directional Microwave Photon with Waveguide Quantum Electrodynamics Aziza Almanakly, Beatriz Yankelevich, Bharath Kannan, Agustin Di Paolo, Alex Greene, Bethany Niedzielski, Kyle Serniak, Mollie E Schwartz, Jonilyn L Yoder, Joel I Wang, Terry P Orlando, Simon Gustavsson, Jeffrey A Grover, William D Oliver Routing quantum information between non-local computational nodes is a foundation for extensible networks of quantum processors. Quantum information transfer between arbitrary nodes is generally mediated either by photons that propagate between them, or by resonantly coupling nearby nodes. The utility is determined by the type of emitter, propagation channel, and receiver. Conventional approaches involving propagating microwave photons have limited fidelity due to photon loss and are often unidirectional, whereas architectures that use direct resonant coupling are bidirectional in principle, but can generally accommodate only a few local nodes. In this work, we develop a quantum interconnect composed of an emitter, receiver, and propagation channel that circumvent issues of prior work. We have demonstrated high-fidelity directional microwave photon emission using an artificial molecule comprising two superconducting qubits strongly coupled to a bidirectional waveguide. Quantum interference between the photon emission pathways from the molecule generates single photons that selectively propagate in a chosen direction. By emitting time-symmetric photons from one module, we operate another identical module tiled along the same waveguide as an absorber of directional microwave photons, developing an interconnect capable of hosting remote entanglement for extensible quantum networks. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A73.00005: A device for routing arbitrary microwave quantum states in waveguide quantum electrodynamics Xi Cao, Abdullah Irfan, Michael Mollenhauer, Supriya Mandal, Wolfgang Pfaff Routing traveling photons in a controlled directional manner is essential for operating a quantum network. Communicating information between arbitrary quantum nodes using itinerant photons requires controllable directionality. In addition, such a network will require high fidelity signal routing and loss resilience. However, implementing such a network in the microwave domain is currently limited by losses due to commercially available directional devices such as circulators and isolators [1-3]. Recent efforts having been made [4] to address this issue and have demonstrated controlled directional emissions of flying qubit states in the 0/1 Fock state basis. Here we present a theoretical proposal that extends this functionality to arbitrary quantum states, such as error-correctable bosonic states. We have designed a parametrically controllable lossless directional device that utilizes the interference between a memory mode and two SNAIL (Superconducting Nonlinear Asymmetric Inductive eLement) modes coupled to a common transmission line. By parametrically tuning the interaction between the memory mode and the SNAILs via microwave pumps, the device can emit and absorb arbitrary photonic wave packets with in-situ tunable directionality and negligible loss. We will present both analytical and numerical analysis for our design, along with preliminary data on parametrically controlling the couplings between the SNAIL and memory modes. Our result demonstrates a powerful design for routing arbitrary quantum states with in-situ control, which will be an enabling component for remote entanglement distribution and state transfer in error-corrected modular quantum networks. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A73.00006: Multimode entangling interactions between transmons coupled through a metamaterial ring-resonator: theory Arne Schlabes, Tianna A McBroom, Xuexin Xu, Jaseung Ku, Bradley G Cole, Britton L Plourde, Mohammad H Ansari The use of Left-Handed-Transmisson lines allows a very high mode denisty at frequencies above the IR cutoff due to its disperson relation. We theoretically support an experiment on coupling two qubits to the device and calculate the g-coupling to the modes, which exhibit different frequency dependency when compared to the right-handed case. A careful analysis of these couplings leads to the effective coupling between the qubits, which can be very large, since the modes are very dense and therefore transmit high interaction. In general this causes the ZZ-interaction between the qubits to be large, but we can still acurately predict static qubit-qubit interaction both for only a few kHz aswell as for tens of MHz. In this talk we will present the modeling of this Left-Handed system and compare it to experimental measurements. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A73.00007: Multimode entangling interactions between transmons coupled through a metamaterial ring-resonator: experiment Tianna A McBroom, Arne Schlabes, Xuexin Xu, Jaseung Ku, Bradley G Cole, Mohammad H Ansari, Britton L Plourde Left-handed metamaterial transmission line resonators made with arrays of superconducting lumped circuit elements have unique dispersion relations resulting in densely grouped mode spectra. Forming these transmission lines into a ring allows access to these densely grouped resonances, but with a compact footprint allowing for flexible design. Superconducting qubits can be coupled to multiple modes in these left-handed metamaterial ring resonators, resulting in a novel landscape of entangling interactions between qubits. We have fabricated and characterized such a device with two superconducting transmon qubits coupled to a left-handed metamaterial ring resonator. We present results characterizing the interactions between the qubit and modes and the interactions between qubits. We find a broad range of g coupling values between the two qubits and modes that mediate the interaction between qubits. The J coupling between the two qubits exhibits high variability depending on qubit detuning and mode proximity. Similarly, the entangling ZZ interaction can be tuned over a wide range. This system thus forms a novel architecture for interaction between qubits through a multimode system. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A73.00008: Towards on-demand, all-to-all connectivity in a superconducting qubit network using a ring resonator based coupler Anirban Bhattacharjee, Sumeru Hazra, Jay S Deshmukh, Meghan P Patankar, Rajamani Vijayaraghavan Increased connectivity in a multi-qubit network is beneficial in minimizing gate count when executing any algorithm. However, it is challenging to avoid coherent errors in fixed coupling architectures due to the cross-Kerr effect between all coupled qubits. We recently demonstrated [1] the use of a ring resonator to provide beyond nearest-neighbour connectivity in a planar architecture with fixed coupling between 3D superconducting transmon qubits. We now extend this work by introducing tunable couplers between each qubit and the ring resonator in a 2D planar architecture. This enables on-demand activation of coupling between any of the connected qubits in the network while avoiding the coherent errors due to the cross-Kerr effect as the unused qubits are isolated from the network. The coupler design is a modification of the popular gmon coupler [2] with a flux biased Josephson junction. We will present the analysis of this coupler design using finite-element simulations and experimental data to validate its operation. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A73.00009: Demonstration of SWAP gate between superconducting and microwave-photon qubits Kazuki Koshino, Kunihiro Inomata We demonstrate a deterministic SWAP gate between a superconducting atom and a single microwave photon propagating in a waveguide, proposed in Phys. Rev. Appl. 7, 064006 (2017). In this scheme, the superconducting qubit is encoded on its ground/excited state and the photon qubit is encoded on its carrier frequency of a single photon, and the SWAP gate is completed by bouncing the photon qubit at a resonator coupled dispersively to the atom. By using a weak coherent-state photon instead of a single photon, we demonstrated bidirectional quantum-state transfer between the atom and the photon. The average fidelity of the photon-to-atom (atom-to-photon) state transfer is 0.829 (0.793) with infidelities due mainly to short lifetime of the superconducting qubit. The present scheme has the advantages of simple setup, in-situ tunability of the gate type, passive atom-photon interaction and dual-rail encoding of photon qubit, and is therefore suited to entangling remote superconducting qubits on different processors. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A73.00010: All-to-all parametric control of a SNAIL-based quantum module Mingkang Xia, Chao Zhou, Evan C McKinney, Jacob J Repicky, Boris Mesits, Alex K Jones, Michael J Hatridge For superconducting quantum computers, the most commonly used architecture is a 2D-lattice architecture with between 2.5 and 4 nearest-neighbors. NISQ algorithms on these machines suffer as the large number of SWAP operations needed to link distant qubits cause long delay, and hence large amounts of decoherence across the processor. An alternate architecture is a modular architecture based on quantum modules and routers. A modular architecture increases the efficiency of NISQ algorithms by using a more flexible and denser network of qubit connection which reduces the SWAP operation count when distant qubits interact. In this talk, we present our work on the basic building block for our modular approach, a 4-qubit module with all-to-all qubit connectivity, controlled with parametric driving. A central SNAIL mode acts as the coupler, creating three-wave couplings among all qubits. Two-qubit gates are realized by driving the SNAIL at the difference frequency of a given qubit pair. Two qubit gates with several hundred ns gate times can be performed between all pairs of qubits. We will present our experiment results on calibrating high fidelity iSWAP gate family on all pairs of qubits in this module and exploring the possibility of implementing more novel types of gates that can improve efficiency at compiling quantum algorithms. We will also discuss the prospects for combining our module with other modules via quantum state routers [1] to build a larger quantum computer. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A73.00011: Demonstration of Dynamically Reconfigurable Long-Range Photon Exchange in a Multi-Qubit Superconducting Quantum Processor Brian Marinelli, Jie Luo, David I Santiago, Irfan Siddiqi We propose and demonstrate a quantum processor (QPU) architecture using superconducting qubits with a reconfigurable qubit connectivity graph. Transverse interactions can be generated between arbitrary pairs of qubits in the QPU with the connectivity graph encoded by the room temperature microwave controls. The reconfigurability is enabled by tunable, time dependent couplings between qubits and a shared tunable Bus resonator (Bus). We implement an 8-qubit version of the proposed architecture and find good agreement between circuit theory predictions and experimental behavior of the tunable Bus element. Qubit-Bus parametric coupling of up to 8MHz is achieved. We further demonstrate qubit-qubit interactions mediated by the Bus within a 5-qubit subset of the device with a maximum coupling rate 0.9MHz and separation of 9.2cm along the Bus resonator. Our work sheds light on opportunities to realize highly connected, reconfigurable QPUs in superconducting circuits. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A73.00012: Implementation of a Quantum Switch with Superconducting Circuits Connie Miao, Gideon Lee, Liang Jiang, David Schuster A quantum switch (QSwitch) is a four-node quantum router that swaps a single photon between an input and two outputs based on a quantum address. In contrast to previous quantum routers, which require the output qubit to be classically selected, a QSwitch can route to a superposition of outputs. A QSwitch is a necessary component for building a quantum RAM (QRAM), as the swap gate that it enables forms the basis of the memory access operation upon which QRAM usage relies. In this talk, we present a QSwitch implemented using four transmons, which to our knowledge is the first experimental demonstration of a QSwitch on any qubit platform. We discuss our memory access gate simulations, which predict a high fidelity operation. We then present our experimental realization of the QSwitch, including its circuit geometry and characterizations of its performance. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A73.00013: Toward high-fidelity inter-chip entanglement between superconducting qubits Michael Mollenhauer, Supriya Mandal, Abdullah Irfan, Xi Cao, Wolfgang Pfaff Modular quantum networks are a promising approach for scaling superconducting quantum processors, due to their potential to avoid crosstalk and to scale beyond a single wafer. An outstanding challenge for the realization of such networks is to achieve high-fidelity inter-chip entangling gates. Inspired by previous results [1-3], we present a modular hardware scheme for performing gates between superconducting transmon qubits on separated chips. We have engineered a low loss, de-mateable superconducting cable connection that we aim to use as a ‘quantum bus’. Combined with parametric drives this approach can achieve high fidelity gates between the qubits, for instance through driving a virtual Raman process. With measured bus quality factors in excess of 100,000 and demonstrated sideband transition frequencies up to 10 MHz, our experimental data suggest that a gate infidelity below 1% in less than a microsecond is within reach. Our inter-chip connection design could thus serve as a key component in a modular, multi-wafer superconducting quantum computer. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A73.00014: Implementation of Fractional State Transfer on a Superconducting Qubit Chain Federico Roy, Maximilian Nägele, Christian Schweizer, Leon Koch, Niklas Bruckmoser, Niklas Glaser, Max Werninghaus, Joao Romeiro, Malay Singh, Gleb Krylov, Stefan Filipp Superconducting circuits are a promising candidate architecture for quantum computation due to their high coherence times and high-fidelity control, however, qubit connectivity is limited to nearest-neighbour local interactions. Nonetheless, recent studies show that simultaneous local interactions can be harnessed to generate multi-qubit operations and efficiently generate many-body entanglement. In this work we operate a superconducting circuit qubit chain, with fixed-frequency transmon qubits, and flux tunable transmon couplers. By simultaneous parametric drive of the tunable couplers we generate effective multi-qubit interactions and transfer excitations from one end of the chain to the other end, an operation known as perfect state transfer. . In this work we implement perfect state transfer on a superconducting circuit qubit chain, where an excitation on one end of the chain is transferred to the other end, based on an effective multi-qubit interaction. Furthermore, we demonstrate fractional state transfer, where only a fraction of the state is transferred, as controlled by the frequency and strength of parametric drives on the couplers. We show how this protocol can be used to efficiently generate entangled states and multi-qubit operations. Finally, good agreement with theoretical predictions suggests the scalability of this protocol to longer qubit chains. |
Monday, March 6, 2023 10:48AM - 11:00AM |
A73.00015: A parametrically programmable coupled oscillator network implemented using microwave superconducting circuits Takuma Makihara, Nathan R Lee, Amir H Safavi-Naeini There is growing interest in networks of coupled optical parametric oscillators (OPOs) for their application as a Coherent Ising Machine (CIM). Despite their success, quantum effects are obscured in these OPO networks due to their large critical photon numbers. We introduce a new superconducting platform for implementing CIMs – the parametrically programmable coupled oscillator machine. Our platform can: 1) implement a variety of Ising couplings in a programmable way, 2) tune its nonlinear to linear loss ratio over a broad range, 3) achieve single-digit critical photon numbers, and 4) be read out easily through microwave lines. The crucial component in our proposal is the Asymmetrically Threaded SQUID (ATS). Unlike most Josephson junction-based circuits that rely on four-wave mixing, the ATS enables the three-wave mixing interaction typically used by OPOs. I will discuss our proposal for using one ATS coupled to many microwave resonators to study how quantum fluctuations change behaviors in CIMs, as well as early experimental results. |
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